Implement control means for tractor operated agricultural implements



Aug. 39, 1966 G. E. SMELCER 3,269,454

IMPLEMENT CONTROL MEANS FOR TRACTOR OPERATED AGRICULTURAL IMPLEMENTS1963 5 Sheets-Sheet l Original Filed July 24 eZcer 5 Sheets-Sheet 2 G.E. SMELCER AGRICULTURAL IMPLEMENTS 1963 fnflent r filen E fi melce?"IMPLEMENT CONTROL MEANS FOR TRACTOR OPERATED Wm m wm Aug. 30, 19%

Original Filed July Aug. 30, 1966 G. E. SMELCER 3,269,464

IMPLEMENT CONTROL MEANS FOR TRACTOR OPERATED AGRICULTURAL IMPLEMENTSOriginal Filed July 24, 1963 .3 Sheets-Sheet 3 i www mi r 93x A @WNN3,269,464 Ice Patented August 30, 1966 3,269,464 IMPLEMENT C(DNTROLMEANS FOR TRACTOR OPERATED AGRICULTURAL IMPLEMENTS Glen E. Smelter,Hinsdale, Ill., assignor to International Harvester Company, Chicago,111., a corporation of New Jersey Original application July 24, 1963,Ser. No. 297,295. Divided and this application June 23, 1965, Ser. No.466,179

9 Claims. ((Il. 172-40) The present application is a division of myco-pending application Serial No. 297,296 filed July 24, 1963 forImplement Control Means for Tractor Operated Agriculture Implements.This invention relates to implement control systems for tractor operatedimplements, but more particularly to improvements in implement depthcontrol mechanisms employed therewith.

Implement depth control mechanisms for tractors operating agriculturalimplements are well known and, heretofore, have been offered in a widevariety of arrangements of apparatus and assemblies. Usually the controlmeans in a mechanism of this character is adapted to respond tovariations in the draft of an attached implement and attendant suchaccompanying change in draft to thereafter effect an adjustment in theoperative relation of the implement to the soil. To accomplish this thesystem was designed to initially sense and then respond to variations inimplement draft, resulting generally from a change in the soilcharacteristics in the immediate area of the implement in the ground, byeffecting a raising or lowering of the implement as necessary tomaintain it at a constant draft relative to the soil being worked.Heretofore such variations in draft on the implement have been sensed bymechanisms utilizing resilient means, usually in the form of springsassociated with either of the links of the implement'attaching hitch.

mechanism, that were reactive for resisting compressive and tensiveforces induced in the link-s by such draft changes and which reactionsthereafter resulted in transmission via suitable linkage means of asignal to an actuator for raising and lowering the implement to conformwith the changing draft demands.

In most of the prior mechanisms the linkage elements and particularlythe pivotal mounting connections thereof were exposed to very severedirt accumulation conditions which ultimately caused either a freeze-upof one or more of these connections or a fracture of some of theelements resulting from excess loads imposed by such conditions. Some ofthese linkage mechanisms also utilized adjustable means in the form of aturn-buckle assembly in the links and these likewise provedunsatisfactory because of a tendency to break or fracture. The aboveconditions also frequently caused the pivotal connections that carriedthe sensing linkage to become heavily loaded or to freeze-up or bind andthus considerably reduced the sensitivity of the sensing mechanism sothat the signal finally transmitted to the actuator did not properlyreflect the degree or magnitude of the draft change on the implement.Additionally, because of the difliculties of economically producingconsistently good springs with identical reactive characteristics thatwere large enough to take the draft load, and because of the erraticfrictional characteristics of the linkages when encumbered by the aboveaccumulation hindrance, plus the space factor complications encounteredon many conventional tractors, the prior solely spring type mechanismshave not been altogether satisfactory. Animportant feature of thepresent invention, therefore, is directed to providing an implementdepth control mechanism that avoids the aforementioned earlier drawbacksinherent in prior mechanisms of this character, and concomitanttherewith providing a more consistently reliable and sensitivemechanism.

The principal object of the present invention, therefore, is to providenew, improved and highly reliable draft sensing means for tractorvehicle-connected groundworking implements.

A general object is to provide an implement depth control mechanismwherein a draft sensing load creates a pressure differential in ahydraulic circuit which the mechanism effectively measures andsubsequently converts a resultant measurement into a signal thatoperates actuator means to adjust the depth of the implement in theground according to the draft load demands being sensed by themechanism.

Another object is to provide draft-sensing means wherein hydrauliccylinder and piston means incorporated in a hitch linkage mechanismemployed for connecting an agricultural implement to a tractor vehicleare operative, responsive to variations in draft loads on the implement,for actuating the vehicles power lift means to effect at raising orlowering of the implement to conform with such changing draft demands,and wherein fluid make-up means are provided to maintain an adequatesupply of fluid at all times during operation in the hydraulic circuitembracing said linkage mounted cylinder.

A further object is to provide for tractor-operated agriculturalimplements a novel implement control mechanism embodying an hydraulicdraft-sensing means that is also operative to provide adjustment andcontrol for the implements operated thereby, and which, because of theself-contained nature thereof additionally may be readily applied to andutilized with conventional tractor vehicles with a minimum ofmodification of the vehicle.

A still further object is the provision of a new and improved implementdepth control mechanism embodying hydraulic draft-sensing means, andincluding there with manually adjustable means for modifying thesensitivity of response of said mechanism to variations in draft loadsbeing sensed by said mechanism.

An important object is to provide an improved draftsensing mechanismwherein a hydraulic cylinder and piston, incorporated in and adapted tofunction as a portion of the linkage, of a hitch linkage mechanism employed for connecting an agricultural implement to a tractor, areoperative for transmitting sensing signals to actuate a power liftmechanism associated with the tractor and which signals reflectattendant pressure differentials created between opposite ends of saidhydraulic cylinder as a result of variations in the draft loads imposedon an associated implement.

A more specific object of the present invention is to provide implementcontrol apparatus for tractor-connected agricultural implements whereinsaid apparatus includes hydraulic means that senses variations in draftloads on an attached implement and thereafter transmits actuatingsignals to a power lift means for adjusting the depth of the implementin the ground attendant said draft variations, and which apparatusadditionally includes manually adjustable means adaptable meansadaptable for overriding the signals of the hydraulic draft sensingmeans and incident thereto limiting the ability of said sensing means tocontrol the operation of the power lift for adjusting the depth of theimplement in the ground.

The foregoing and other objects and features of the invention willbecome apparent as the disclosure is more fully made in the followingdetailed description of a preferred embodiment of the invention asillustrated in the accompanying sheets of drawings in which:

FIGURE 1 is a fragmentary and generally diagrammatic view, partially insection, of a tractor equipped with 3 an implement depth control systemembodying the features of the invention;

FIGURE 2 is a generally schematic view, with portions thereof insection, showing the components embodied in the proposed implementcontrol system, and including illustrated details of the means providedfor adjusting the sensitivity of response of the draft sensing apparatusportion thereof;

FIGURE 3 is a vertical sectional view taken generally along the line 3-3of FIGURE 2;

FIGURE 4 is a fragmentary horizontal sectional view taken generallyalong the line 4-4 of FIGURE 2;

FIGURE 5 is a fragmentary horizontal sectional view taken generallyalong the line 55 of FIGURE 2;

FIGURE 6 is a view generally similar to FIGURE 1 but showing a modifiedarrangement of the application of the invention; and

FIGURE 7 is a fragmentary plan view of the modified arrangement shown inFIGURE 6;

Referring now to the drawings, it will be noted that the proposedimplement control arrangement has been shown as applied to and utilizedwith a generally conventional type of tractor vehicle which vehicle isdesignated in its entirely by the reference numeral 10. The rear axleand differential housing frame portion 11 thereof, in this applicationof the device, has a pair of transversely spaced lower draft links 12(only one of which appears in the drawings) universally pivoted theretoat 13, for movement, principally, in a vertical plane, and about axeslocated below the axis of the rear axle of the vehicle. A third or upperor top draft link 14 is pivotally connected through the universal pivot15 and bracket 16 to the upper rear portion of housing frame 11. Thelower and upper links 12, 14 extend rearwardly from the tractor andconstitute one form of what is generally termed an implement attachinghitch or hitch linkage mechanism. At their outer ends the links areadapted for connection, respectively, with upper and lower portions of avertically extending mast member 17 that may constitute a portion of animplement frame 18. The attached earthworking implement depicted hereinis a plow and the frame 18 has extending downwardly therefrom a beamlikemember 19 which supports the plow bottom indicated generally by thenumeral 20.

The lower or sometimes called draft links 12 are arranged to be movedvertically usually by suitable power means which, as illustrated,comprises a pair (only one of which appears in the drawings) of liftarms 21 constrained for rotative movement with and secured one each toopposite ends of a rockshaft 22 and each of which arms, in turn, isconnected by a drop or lift link 23 with a respective one of said draftlinks. The rockshaft 22 which extends transversely of the housing frame11 has securedly aflixed thereto a crank arm 24 through which saidrockshaft is rocked to lift or lower the arms 21 by a hydraulic motorthat includes a cylinder 25 and piston 26, with said piston and crankarm 24 being coupled by the connecting rod 27. Pressure fluid issupplied to the lift cylinder 25 from a suitable pump, such as indicatedat 28, which, in turn, may be connected by conduits 29 and 30 with theflow of fluid to and from said cylinder controlled by an actuatorcontrol valve indicated generally at 31.

The pump 28 may be mounted within the housing frame 11 and a reservoir30a may be fashioned as an interior compartment or chamber area formedas part of a housing embracing the hydraulic lift cylinder and theactuator valve therefor, as is well understood, hence, it is believed nofurther structural details thereof need be illustrated herein. Actuatorcontrol valve 31, which may be of conventional or well knownconstruction, preferably, but of the type disclosed in US. Patent No.2,716,- 966, issued September 6, 1955, to Clarence A. Hubert and JosephF. Ziskal, and is operative selectively to permit delivery of fluidunder pressure through a passage to one end of the lift cylinder whilesimultaneously opening another passage for escape of fluid to thereservoir from the opposite end of said cylinder in order to lift thelower draft links 12, and vice versa in order to lower said draft links,or to provide a neutral position wherein the passages to both ends ofsaid cylinder are blocked and the associated circuit is closed.

Now, in accordance with the more specific teachings of the invention,according to one preferred embodiment as illustrated herein, the upperor top draft link 14 is fashioned with a forward link portion 14apivotally mounted at 15 on the bracket 16 in turn suitably affixed tohousing 11, and with its opposite end fixedly secured to the casing ofan auxiliary hydraulic cylinder 32, while a rear link portion 14bpivotally connected at one end thereof to the upper end of a mast 17 hasits opposite end connected to a piston 33 slidably operative within thecylinder 32. The rear link portion 141) thus functions, in effect, as aconnecting rod for piston 33. Suitable sealing means, such as the ringsshown at 34, may be provided in one end of cylinder 32 for cooperationwith link connecting rod 14b, while, preferably, high-pressure flexiblehose conduits 35, 36 are connected by suitable fittings 35a, 36a torespective ends of the upper link or auxiliary cylinder 32. The oppositeends of said flexible conduits are connected to suitable fittings suchas 35b, 36b respectively, which, in turn, are connected by conduits 37,38 to opposite end portions of a casing or housing 39 of a draftsignaling control valve unit designated generally by the referencenumeral 40.

Valve housing 39 is fashioned with a bore 41 extending longitudinallytherethrough that slidably accommodates a relatively small-diameterpiston 42 therewithin. One end or face of said piston has suitablyaflixed thereto and projecting therefrom guide rod 43, which extendsthrough an aperture 44 in an end wall of valve housing 39 and has formedon the outwardly projecting end thereof .an enlarged head or upset endportion 45 while a spring 46 coiled around said guide rod is abuttinglypositioned between the head 45 and the proximate end wall of said valvehousing. Suitable sealing means such as the rings 47 may be provided torestrict fluid flow along the guide rod 43 as is well understood. Theopposite end or face of piston 42 has suitably .aflixed thereto andprojecting therefrom a plunger member 48 which extends through anaperture 49 in an opposite end wall of said valve housing and hasprovided thereon proximate the outwardly projecting end portion thereofan abutment head or collar 50, while a coiled spring 51 seated on saidcollar and positioned over said plunger is compressibly reactive againstthe latter collar and the proximate end wall of housing 39. Suitablesealing means such as the rings 52 may be provided to limit fluidleakage axially along the plunger member 48. Extending upwardly from oneside of valve casing 39 is a pedestallike portion or projection 53 and aplate-like support member 54 is removably secured to the outer end ofsaid projection by suitable securing means such as the cap screwsindicated at 55. Securedly positioned on the support member 54, by anysuitable means such as the bolts 56, is a by-pass valve, operative topermit tilt ladjustment of the implement and indicated generally at 57,which comprises a cylinder-like housing 58 with a bore 59 extendinglongitudinally therethrough and having oppositely disposed ports 60, 61,connected respectively, by conduits 62, 63 for by-pass or fluidcommunication with fittings 35b, 36b, and a piston 64 slidably disposedin said bore with a plunger rod 65 vafiixed to and extending upwardlyfrom one end of said latter piston. A radial aperture 66 extendingthrough piston 64 is provided for a purpose which will presently befurther explained. A cover plate 67, with an opening 68 therethrough toaccommodate plunger rod 65, may be suitably secured as by the bolts 69to the upper end of cylinder housing 58, and a sealing ring 70 may beprovided in said cover plate opening to restrict fluid leakage axiallyalong said plunger rod. A coil spring '71 encircling plunger 65 isseatably positioned between the cover plate 67 and a stop collar orwasher 72 positioned on said plunger and constrained, against axialmovement in one direction, by a pin or cotter key such as 73 suitablysecured in said plunger. The spring 71 is positionably dimensioned andstressed to normally urge piston 64 upwardly so that the aperture 66therein is not in registering alignment with the oppositely disposedport openings and 61 whereby the free flow of fluid between conduits 62and 63 is restricted.

A shell-like housing or support structure indicated in its entirety bythe reference numeral 75, may be fashioned to include an outer perimeterwall 76, an inner closure wall 77 to which said outer wall is affixed,and a plurality of lugs or brackets 78 adapted to receive fastening boltmeans 79 whereby said structure may be mounted on a side wall portion ofthe vehicle housing frame 11. Said structure may, if desired, beprovided as a container-like support for components of the proposedmechanism and a suitable cover plate (not shown) provided for coveringthe contents so as to protect them against excess exposure to dirt anddebris. Suitable conventional mounting means, such as the brackets 40aand fastening bolt means indicated at 40b, may be provided for mountingthe valve 40 and its associated components within said containerstructure, so that said structure along with its components may be addedto the vehicle as a unit or packagelike assembly.

The plunger rod extends through an aperture 74 in the upper wall portion76, of support structure 75, and a suitable sealing and lubricatinggland or bushing such as indicated at 80 may be provided thereof as iswell understood for such uses. The outwardly projecting end of plungerrod 65 engages a manually operable control or handle member 81 pivotallymounted at 82 on a bracket 83 supportably carried by and suitablyaffixed to the upper wall portion 76 of said support structure. Thepivotal connection 82 may include any well-known friction or detentmeans (not shown) suitable for resisting movement of control handle 81out of a preselected position except when manually motivated out of suchposition. Since such frictional and detent means are conventional and sowell known for similar purposes, it was felt a full description of thestructural details of a specific such means herein was unnecessary.

It will be appreciated, of course, that the bypass valve unit 57 couldbe fashioned as an integral part of the housing 39 without deviatingfrom any of the inventive concepts hereof.

The outwardly projecting end of plunger member 48, of signaling valve40, is fashioned with a recess or cutaway area 84 (FIG. 5) and has astud or pin 85 mounted thereon which extends into said recessed area andpivotally supports a roller 26 retained on said pin by suitable meanssuch as the cotter key or pin 87. Spaced axially outwardly from saidstud and securedly affixed to plunger member 40 is a large-headed pin orstud 88, the head of which also extends into said cut-away area. Theroller 86 and pin 88 as thus disposed serve as a cam follower and guideor cam operating means, as will subsequently be more fully understood.

A generally wedge-shaped plate-like cam member 89 with opposite edgescontoured to provide cam profiles substantially as illustrated, has anover turned edge portion 90 providing a track that is dimensioned forpositioning between the cam engaging roller 86 and guide pin 88 wherebymovements of plunger 48 and cam 89 may be operatively coordinated in apositive cam and follower relationship. The cam-plate member 89 isfixedly se cured to a vertically positioned support member 91 whoseopposite ends have afiixed thereto and extending transversely thereofupper and lower roller carrying brackets 92, 92a, respectively. Each ofsaid roller carrying brackets has suitably supported thereon a pair ofspacedapart identical spindles or studs, such as indicated by thereference numeral 93, which, in turn, journals a respective rollermember 94. An enlarged head or upset portion such as 94a suitablyprovided on the free end of each spindle serves to retain a respectiveroller member thereon. A cam member support frame, indicated generallyat 95 (FIGURE 3), comprises an outer generally C-shaped member 96 and asmaller oppositely facing generally D-shaped inner member 97 (with oneside thereof open) positioned therewithin, and affixed thereto by anysuitable means such as the welds indicated at 98, with said membersdisposed so as to provide upper and lower tracks 99, 100 each of whichslidably accommodates a set of two rollers 94. A support frame mountingand guide rod 101 has one end thereof suitably secured to said camsupport frame for movement therewith while an opposite or upper endportion of said rod projects through an aperture 102 in upper wallportion 76, of housing structure 75, and a suitable sealing andlubricating gland or bushing such as indicated at 103 may be providedthereat as is well understood. The outwardly projecting end of guide rod101 has a large-headed pin or stud 104 therein that serves as a camfollower and is positioned so that the head thereof extends into a camguide track 105 fashioned in an arm of a manually operable controlmember or handle 107, in turn, pivotally mounted at 108 on the bracket83. Cam guide track 105 may be contoured to provide the desired positionrelation for sensitivity lever 107 and, preferably, will be fashioned asa smooth curve except for detent notches 106 which serves to locate andmaintain the No Effect Zone of cam 89 in alignment with roller 117. Itis understood, of course, that suitable friction means (not shown) orother suitable means for fixedly positioning the adjusted verticallocations of cam track 105 will be provided to normally maintain saidcontrol member in any rotatively selected position, as is wellunderstood.

The opposite or forwardly facing end edge of cam member 89 has a loweredge portion thereof overturned to provide an inclined cam track 109,while disposed above said latter track is another track, indicatedgenerally at 110 and designated as the draft control operating rangeportion or area of the mechanism, that is formed between the divergingridge or rib members 111, 112 which, in turn, extend outwardly from theface of cam plate 89. Said ridges or ribs may be formed integral withsaid cam plate or separately fashioned and suitably secured to said cammember, as is well understood, without deviating from any teachings ofthe inventive concept hereof. As shown, the track 110 somewhat generallyconforms in camming configuration, although it is not limited thereto,to the track profile provided by end edge portion 90, but it will benoted that the side walls of track 110 diverge so that the lower portionof the track is wider than the upper portion thereof for a reason whichwill presently become apparent. An actuator control rod 113 slidablymounted in an aperture 114 in perimeter wall 76 has one end thereofcut-away or recessed at 115 and a. stud or pin 116 mounted thereonextends into said recessed area and pivotally supports a roller 117suitably retained thereon. The roller 117, in turn, is positionablebetween the ridges 111, 112 and, under certain circumstances, adaptedfor contacting engagement with one or the other of said ridges or, withboth of said ridges simultaneously, while at other times with cam track100, and as thus engaged may be made to follow with varying degrees ofcontrol, the movements of said cam member; while at still. other times,no engagement occurs with either of said tracks. A boss 118 provided onwall 76 adjacent aperture 114 includes an extension of said aperture forslidably accommodating the rod 113, and a threaded opening 119 in saidboss receives a bearing shoe and a spring 121 held in place by a setscrew 122. The spring 121 urges bearing shoe into frictional engagementwith the rod 113 while the set screw 122 is adjustable to vary thedegree of such fric- 7' tional engagement, all for purposes which willpresently be readily understood.

The actuator control valve 31 which may be conventional in structure,preferably, is of the type disclosed in the noted U.S. Patent No.2,716,966 and wherein, as illustrated in the present invention, the liftcylinder and the actuator control valve 31 are disposed in closeproximity to one another in a casing-like structure such as isrepresented herein by the reference numeral 130. Since the operation ofthe control valve and lift cylinder of the present invention issubstantially identical to that disclosed in the above referenced US.patent no further elaboration of the structural details thereof need beincluded herein. In the instant invention the actuator control rod 113,which constitutes a part of the signal input means to the actuatorcontrol valve, is normally directly operative responsive to movements ofthe cam member 89 instead of to the operators control handle as is thecase in said patent structure, otherwise the functioning of the twostructures is identical.

It will be apparent to those skilled in the art that an actuator controlvalve, such as indicated at 31, of the type disclosed in the previouslyreferenced U.S. Patent No. 2,716,966 is readily adaptable to provide foradmission of fluid into only one end of the lift cylinder 25 in order toraise the implement, while depending upon the weight of the implement toeffect the lowering thereof, without deviating from any of thefundamental teachings of the present invention. In such event, it willbe understood, certain modifications would also be made in the cammember 89 as presently illustrated in order to coordinate the movementsthereof with the operation of valve 31, all of which is well within thepurview and bounds of the present invention.

The opposite or outwardly extending end of rod 113 is connected to ahead 123 which is pivotally mounted at 124 on a walking beam link member125 proximate one end of said link. The opposite end of said walkingbeam link is pivotally connected at 126 to a bracket 127 constrained formovement with the lift cylinder connecting rod 27. Intermediate the endsthereof the walking beam link 127 is pivotally connected at 128 to theoutwardly projecting end of the control element spool or plunger 129 ofthe actuator control valve 31.

A pressure relief and bleed valve, indicated in its entirety at 131, isconnected by conduit 132 to a port 133 opening into bore 41 while theopposite end of said valve communicates by conduit 134 with a hydraulicfluid supply reservoir indicated herein at in housing 138. It will beappreciated, of course, that any other suitable fluid supply reservoiron the vehicle could be used for this purpose. Relief valve 131, whichis generally conventional in structure, includes a ball member 135 thatengages a valve seat 136 and is urged thereagainst by a spring 136awhich spring is stressed so as to constantly permit a small amount offluid from bore 41 to bleed past the seat 136 under normal operatingconditions, but will permit full flow exhaust into the reservoir whenexcess pressure occurs in the latter bore as is well understood.

A combination fluid make-up and surge restricting valve means, indicatedgenerally at 137, communicates by way of a port passage 138 opening intobore 41 and by way of conduit 139 with the pressure side of pump 28. Acasing 140 having a bore 141 therein accommodates a ball 142 which mayengage either one or the other of oppositely facing valve seats 143, 144fashioned therewithin, and a plunger 145 has one end thereof adapted toengage said ball while the opposite end of the plunger is affixed to acruciform-shaped spider 146 having a small guide plunger 147 on theopposite side thereof. A spring 148 positioned around plunger 147 seatsagainst spider 146 and one end of casing 140, while an aperture in saidcasing is aligned and coterminous with port opening or passage 138.Suitable means (not shown) Will, of course, be provided for aflixing themake-up valve 137 to the draft signaling valve 40 when they areseparately fashioned. It will be appreciated, also, that the casings ofthese valves may be integrally fashioned as well without deviating fromany of the inventive concepts hereof. During normal operation the spring148 is stressed to permit the pressure in conduit 139 to cause the ball142 to assume a position out of engagement With the valve seats 143 and144 and thereby allow fluid from pump 28 to flow into bore 41. When thisarea is filled and no additional make-up fluid is required the excesswill bleed off to the reservoir through the combination bleed and reliefvalve 131. However, in the event a surge occurs in the main hydrauliccircuit being supplied by pump 28 the excess pressure thus created willcause ball 142 to engage valve seat 143 and prevent this excess surgepressure being transmitted into bore 41. On the other hand, when a surgeoccurs in bore 41 ball 142 engages valve seat 144 and closes 01f conduit139 to this excess surge pressure. Also, when the pressure in thecharging circuit 139 falls below normal, ball 142 will seat againstvalve seat 144 and thus prevent loss of fluid from the closed circuitembracing bore 41. Such pressure decrease will also permit relief valve131 to close and stop fluid bleed ing until the charge pressure hasreturned to normal. Any loss of fluid in flexible conduit 35, conduit 36and the opposite end of bore 41 can be made up by momentarily openingthe by-pass valve 57. This arrangement, it will be appreciated, permitsthe proposed hydraulic draft sensing mechanism circuit to be tied intothe main fluid charging circuit of a vehicle without requiring the useof a separate fluid pressure supply for the draft sensing circuit. Ifdesired however, a separate fluid pressure supply might be provided forsaid draft sensing circuit in which case the valve 137 would beunnecessary and could be replaced with a conventional unidirectionaltype of check valve that would permit only the inflow of fluid to thedraft signaling valve 40.

In FIGURES 6-7 there is illustrated a modified application of theproposed implement depth control mechanism. The modification therein isdirected to the environmental application illustrated and isparticularly related to the adaptation of the proposed control mechanismto a different form of earth-working implement and to the trail-behindhitch mechanism employed for attaching implements of that particulartype to its associated vehicle. In the modification, parts and elementsidentical to those of the initially described preferred form, shown inFIGURES 1-5, have been referenced with the same reference numeralsemployed therewith, while comparable parts or components which althoughsimilar are not identical are referenced generally with similarreference numerals, Whenever feasible, but in the 200 series ofnumerals.

In the modified arrangement the tract-or vehicle 10 includes a rear axleand differential housing frame portion 11 to which is affixed atopposite sides thereof, by suitable means such as the bolts 213, aU-shaped fixed drawbar 212. Apertures 212a spaced along the transverseportion of said drawbar are provided to accommodate the pin portion 215aof a universal pivotal connection 215 and said pin may be retained inposition by suitable lynch pin means such as shown at 21512. A draftlink assembly 14 has a forward link portion 14a that has one end thereofattached to the fixed drawbar 212 by means of the universal pivotalconnection 215 while the opposite end of said link portion is fixedlysecured to the casing of an auxiliary cylinder 32, and a rear linkportion 14b is connected at one end to a piston 33 slidably operativewithin cylinder 32 while the opposite end of said portion is pivotallyconnected at to a tool bar frame indicated in its entirety at 218. Itwill be understood, of course, that the latter connection could be ofthe universal type if desired without deviating from any of theteachings of the present invention. The universal pivotal connection 215is arranged to permit full pivotal movement of the draft link 14 in ahorizontal plane and incidental movement in a vertical plane, while thepivotal connection 140 permits full vertical movement of the tool barframe 218 relative to said draft link and, when said latter connectionis of the universal variety, incidental movement in a horizontal plane.

Suitably attached, as by the detachable connecting or clamping meansindicated generally at 219, to and depending from the frame 218 are aplurality of transversely spaced-apart subsoiler implements showngenerally by reference numeral 220. A transversely extending tubularrockshaft member 222 is journaled at opposite ends thereof by suitablemeans such as the journal brackets 222a (only one of which is shown)mounted on the frame 218 and attached thereto by bolt means 22217.Aflixed to and extending from the rockshaft 222 are a pair (only one ofwhich appears) of transversely spaced wheel-carrying lift crank armmembers 223 each of which rotatably mounts a support wheel 223a. A crankmember 224 mounted by suitable aflixing means on rockshaft 222 extendsupwardly therefrom and is pivotally connected by the pivotal clevismeans indicated at 224a to the outwardly projecting end of the liftcylinder connecting rod 27, which is previously described, is connectedto the piston slidably mounted in the lift cylinder that comprises thehydraulic actuator motor which is actuable for rocking shaft 222 andthereby raising and lowering the associated subsoiler implements 220.

The hydraulic actuator motor, as previously mentioned, along with theactuator control valve therefor are included in the unit assemblyindicated generally at 13% and which is connected by the flexibleconduits 29 and 30 to the hydraulic pump indicated at 28. The draftsignaling control valve mechanism along with the sensitivity adjustingand motion-transmitting camming means plus the appropriate controlstherefor are included, as previously described, in the shell-likehousing or support structure, indicated by the reference numeral 75, andis communicatively connected to the auxiliary cylinder 32 by way of theflexible high-pressure conduits 35 and 36. A platelike bracket orplatform support member 225 carried by the tool bar frame 218, andsecured thereto by suitable fastening means such as the bolts and nutsindicated at 225a, may be provided to supportably mount the units and130 thereon while any well known mounting means such as the brackets andbolts indicated at 2251; may be utilized to aflix said units securelythereon.

As previously described the actuator control rod 113 extending outwardlyfrom the unit 75 pivotally connects with the walking beam link member125 which, in turn, pivotally connects with the plunger 129 of theactuator valve and with the lift cylinder connecting rod 27.

Operation In operation, manual movement of the control handle 107 ineither direction will, under certain positions of cam member 89, incur acorresponding movement of the piston 26 of the hydraulic motor or ramcylinder 25. For instance, a forward or upward movement of the upper endof control handle 107 will, acting through the cam track and camfollower pin 104, cause vertical downward movement of guide rod 101 andits attached cam support frame 95 which carries with it the cam member89. Since the cam 89 is restricted against rearward lateral movement bythe spring 51, of draft signaling valve 40, and when the cam member 89is in the draft control operating range thereof and hence at anelevation such as to permit the ridge 111 of cam track to close the gaptherebetween and then engage follower roller 117 this will effectforward movement of the actuator control rod 113 which thereupon causescounterclockwise swinging of the walking beam about the then fixed pivot126 and endwise movement of the actuator control valve spool or plungerelement 129 forwardly or to the right as viewed in FIG- URE 2. Thisforward movement of said control valve element will cause fluid to beintroduced into the right end of cylinder 25, in a manner readilyunderstood from a perusal of the operation of said referenced US.patent, whereupon the piston 26 is moved rearwardly to raise or lift theattached implement and carrying with it the upper end of walking beam125 and in this manner causing said walking beam link to pivot about itsthen fixed pivot 124 until the actuator control valve spool or plungeris moved rearwardly and returned to its initial or neutral position.

Movement of the control handle 107 counterclockwise under similarconditions and with cam member 89 in its draft-control range, will causea vertical upward movement of guide rod 101 and its associated camsupport frame 95 together with said cam member. Since cam member 39 isrestricted against free lateral movement by spring 46, of signalingvalve 40, and with said cam member at an elevation to permit suchengagement, and since cam track 90 inclines rearwardlly said cam memberwill move laterally rearwardly on rollers 94 as it is elevated,whereupon ridge 112 of cam track 110 after closing any gap between saidridge and its engageable follower roller 117 will effect a rearwardmovement of the actuator rod 113 which thereupon causes a clockwiseswinging of the walking beam 125 about the then fixed pivot 126 andendwise movement of the control valve spool control element 129rearwardly or to the left, as viewed in FIGURE 2. This rearward movementof the valve control element willd cause fluid to be introduced into theleft end of the cylinder 25 whereby the piston 26 is moved forwardly tolower or drop the implement and carrying with it the upper end ofwalking beam link 125 and in this manner causing said walking beam linkto pivot about its then fixed pivot 124 until the control valve spool orplunger is moved forwardly and returned to its initial or neutralposition.

Normally the bypass or tilt valve 57 is positionably conditioned forrestricting free flow of fluid therethrough with the components thereofbeing disposed substantially as illustrated in FIGURE 2. However, in theevent it becomes desirable to utilize this advantageous and simplefeature of the invention for adjusting the tilt or angular displacementof the implement, as illustrated in FIG- URES 1 and 2, the controlhandle 81 is manually manipulated to move the plunger rod 65 downwardlyagainst the reaction of spring 71 thereby effecting a positioning ofaperture 66, in piston 64, into registering alignment with port openings60 and 61 so as to permit free fluid communication, by way of conduits62, 63 between opposite sides of cylinder 32 in the upper link 14. Underthis condition said upper link may be readily adjusted by manualmovement thereof to any preselected length required to provide thedesired implement tilt. When the desired length for link 14 has beenattained control handle 81 is returned to its initial position whereuponspring 71 reacts to raise piston 64 to its original position and in sodoing interrupts fluid communication between ports 60 and 61, thuscausing the elements of link 14 to tend to function as a substantiallyrigid non-yielding member instead of as a telescoping structure uponapplication thereto of tension and compression forces by the attachedimplement.

Assume now that the implement has been lowered to its desired workingdepth in the soil whereupon the draft thereof will be balanced againstthe difference in forces set-up thereby between opposite faces of thepiston 42, in valve 40, and said implement will continue to function atthe selected depth so long as the draft load thereon does not vary. Uponencountering a variation in soil density or some other circumstancewhich causes an increase in draft load, the implement will tend to swingupwardly either about the pivots 13 or about the pivotal connections ofmast 17 with the lower draft links i1-2. This action produces a forwardmovement of the rear link portion 14b which thereupon tends totelescopingly compress upper link 14. This results in an increasedcompressive force in said upper link which thereupon tends to urgepiston 33, of cylinder 32, forwardly or to the right as viewed herein,thus forcing fluid from the right end of said cylinder through conduits35, 37 into the left end of bore 41, of valve 40, where such fluidreacts against the left face of piston 42 endeavoring to overcome thereactive resistance thereto of spring 46 and the reaction of the fluidon the opposite face of piston 42. However, since the pressure inconduits 36, 38 is simul taneously reduced upon an inward movement ofpiston 33 the difference in pressure between opposite ends of saidcylinder thus becomes effective to accomplish movement forwardly, or tothe right, of piston 42 within the bore 41 and likewise of its attachedplunger member 48.

Since the effective diameter or exposed face or pressure area of piston33 is much greater than the corresponding face of piston 42 this resultsin an increased mechanical advantage whereby a very small lateralmovement of piston 33 produces an appreciable correlated lateralmovement of piston 42. This feature is particularly advantageous sinceit permits a very small as well as a large change in draft to be readilysensed and registered and subsequently reflected by way of a muchgreater lateral movement in the signal transmitting elements of thedevice, thus the device is made materially more sensitive and.susceptible for sensing and correcting for small as well as largevariations in the draft load. Inasmuch as the roller 86 and pin 88 onthe end of plunger 48 are in contacting engagement with opposite facesof track 90, of cam member 89, and vertical movement of said cam memberrestrained by the frictional holding means of handle 107, any lateralmovement of plunger 48 will incur a comparable movement of said cammember. When the cam member 89 in the draft control range thereof hastraveled a horizontal distance suflicient to close any gap betweenfollower roller 117 and ridge 1111, of cam track 110, said roller willpickup the signaling movement being transmitted through cam member 89and transmit it by way of actuator control rod 113 to the actuatorcontrol valve 31. In the present instance, this will cause walking beamlink member 125 to swing counterclockwise about pivot 126 therebyeffecting a lifting or raising of the implement which thereupon causes adecrease in the draft on said implement.

In a similar manner when a condition is encountered which results in adecrease in draft load the implement tends to swing downwardly or rotatecounterclockwise about its pivotal connections. This produces a rearwardmovement of the rear link portion 14b which thereupon tends to elongateor stretch the upper link '14 and incident thereto to place said link intension. This action tends to urge piston 33, of cylinder 32,rearwardly, or to the left as viewed herein, thus forcing fluid from theleft end thereof through conduits 36, 38 and into the right end of bore41, of valve 40, where such fluid reacts against the right face ofpiston 42 endeavoring to overcome the reactive resistance thereto ofspring 51 and the reaction of the fluid on the opposite face of saidpiston. Since the pressure in conduits '35, 37 is concomitantly reducedupon such movement of piston 33 the difference in pressure betweenopposite ends of said cylinder thus becomes effective to accomplishmovement rearwardly of piston 42 and its attached plunger member 48.Since roller 86 and pin 88 on plunger 48 are in engaging contact withopposite sides of track 90, of cam member 89, which is restrainedagainst vertical movement, any lateral movement of plunger 48 will incura similar movement of said cam member. With cam member 89 in the draftcontrol range thereof, when the gap between roller 117 and ridge 112, ofcam track 110, has been closed said roller will then pick-up thesignaling movement being transmitted thruogh cam member 89 and transmitit by way of actuator control rod 113 to the actuator control valve 31.In this instance, such movement will cause walking beam 125 to swingclockwise about pivot 126 12 thereby effecting a lowering or dropping ofthe implement which thereupon reestablishes the desired draft load onsaid implement.

The operation of the modified arrangement illustrated in FIGURES 6 and 7is generally similar to the embodiment shown in FIGURES 1-5. Asheretofore explained in detail, in describing the operation of thepreferred form illustrated in FIGURES 1-5, the control handle 107 may berotated to cause actuation of the lift cylinder for rocking rockshaftwheels 223a and in that way conversely lower and raise the earth-workingimplement 220 to vary the depth thereof in the ground. Now assume, asbefore, that the implement 220 has been lowered to its desired workingdepth in the soil and the draft load thereon balanced against thedifference in forces set up thereby between opposite faces of the pistonin the draft signaling valve contained within the unitary assembly 75,whereupon said implement will continue functioning at the selected depthuntil encountering a variation in draft l-oad thereon. Upon encounteringan increase in draft load, the implement while tending to swing or pivotabout its pivotal connection 140 will at the same time tend to elongatethe draft link 14 by producing a rearward movement of the rear linkportion 14b thereof. Since link portion 14b is constrained for movementwith piston 33 a rearward movemen-t of said piston operates to forcefluid from the left end of auxiliary cylinder 32 out through conduit 35and into one end of the draft signaling valve contained in unit where,as previously related, this produces an increase in pressure in one endof the valve and causes a forward movement of the plunger thereof. Thislatter movement, in turn, produces a forward movement of actuatorcontrol rod 113 which transmits such movement .signal by way of theinterconnected spool plunger 129 to the actuator control valve in unit130 which then responds to actuate the hydraulic lift cylinder and tolower the support wheels 223a and thereby raise the implement so as todecrease the draft load thereon. It will be apparent from the above thatin the modified arrangement an increase in draft load produces arearward movement of piston 32 in auxiliary cylinder 33 whereas in theother preferred embodiment such increase produces a forward movementthereof, but this is readily compensated for by reversing the conduitconnections 35 and 36 between the cylinder and unit 75 without deviatingfrom any fundamental teachings of the invention.

Next assume a condition which results in a decrease in draft load. Inthis case the rearward urging of the implement is decreased whereuponthe fluid pressure in the left end of auxiliary cylinder 32 is able toreact and effect a forward movement of piston 33 and hence a shorteningof draft link 14. This movement produces an outflow of fluid from theforward end of said auxiliary cylinder by way of conduit 36 into theforward end of the draft signaling valve which thereupon produces anincrease in pressure in this end of said valve and such increase causesa rearward movement of the plunger thereof. Said latter movement, inturn, causes a rearward movement of actuator control rod 113 whichtransmits such movement signal by way of the interconnected spoolplunger 129 to the actuator control valve in unit 130 which thenresponds to actuate the hydraulic lift cylinder and to raise the supportwheels 223a and thereby drop the implement so as to re-establish thedesired draft load on said implement.

It will be seen from the foregoing that the proposed mechanism is highlyeffective for maintaining a substantially constant draft load on theimplement, and because of the mechanical advantage developed thereinprovides an apparatus that is highly sensitive for registering andcorrecting for implement draft variations of minimum as well an maximummagnitudes. It will also be appreciated that a very simple means hasbeen incorporated in the mechanism for adjusting the length of the upperlink of the hitch and concomitant therewith altering the angle or tiltof an implement in the soil.

It will be noted that the opposite ridges 111, 112 of cam track 110diverge from one another so that the lateral dimension of cam track 110changes considerably from one end to the other thereof, and that onlyadjacent the upper end thereof does the roller 117 contactingly engageboth said ridges at the same time. The purpose of this arrangement is toprovide for variation in the degree of sensitivity or magnitude of draftload change required to effect response of said mechanism. For instance,when the cam track 110 is in such position that both sides thereofsimultaneously contact roller 117 any lateral move ment of cam member 89will immediately be transmitted to the control valve 31 to effect anappropriate correction in the elevation of the attached implement.However, there are circumstances When,'because of frequentirregularities of ground contours or frequent changes in soil density orother similar conditions, it becomes desirable to provide variablesensitivity or varying degrees of magnitude of draft load change toeffect response of the device in order to reduce the frequency ofcorrections being effected. This is readily accomplished in the presentinvention merely by rotating the control handle 107 and thereby changingthe elevation of the cam member 89. This has the effect of modifying thepoint of engagement of the roller 117 with the appropriate ridge of camtrack 110 and thereby providing in effect a lost-motion connectiontherebetween. By decreasing the gap or spacing between the roller 117and its respective engaging ridge member the sensitivity is increased ormagnitude of draft load change required to efiect response is decreased,and, conversely, by increasing this gap or spacing the sensitivity isdecreased or magnitude of draft load change required to effect responseis increased.

Referring to FIGURE 2 of the drawings, it will be seen that anintermediate portion of the right hand side of cam member 89 is devoidof any cam or ridge member that is engageable with roller 117. This istermed the No Effect zone or null area and when the cam member 89 is sopositioned that roller 117 rests in this No Effect zone any lateralmovement of said cam member will produce no comparable movement of saidroller, hence the control valve 31 will not be operatively responsi veto such movements. The friction bearing shoe or block 1241 creates afriction on actuator rod 113 which resists axial movement of said rodwhich is such that it can be overcome by movement of cam member 89 butcannot be overcome by movement of the Walking beam member 125. This, ofcourse, is particularly useful when the roller 117 is disposed in the NoEffect zone of cam member 89.

The cam track 109 provides a manual over-ride means for lowering theimplement. When the cam member 89 has been raised to a position suchthat the roller 117 is disposed in the No Effect zone of said cam memberthe vertical alignment thereof will be such that the lower edge of ridge112 of track 110 may, under some circumstances of draft load or the lastused lift position, interfere with a lowering of the cam member 89 whenit is desired to reposition said roller within the draft control rangeof cam track 110. Hence, in order to accomplish this the cam member 89is first raised by control handle 107 until roller 117 engages track 109and moves said roller leftwardly a distance sufficient to permit itsreentry into cam track 110 when said cam member is subsequently loweredby manipulation of said control handle.

Although only preferred embodiments, which show the invention utilizedin association with an upper link element of a hitch linkage, and with adraw-bar type single point linkage have been illustrated and describedherein, it will be appreciated that it is not limited to suchapplication since it may readily be applied to lower link elements aswell as to other draw-bar types of hitch installations with equalfacility without deviating from any teachings of the inventive conceptshereof.

Variants in individual components of the mechanism disclosed willreadily occur to skilled designers in the field. Accordingly, eventhough a particular embodiment and application of the invention has beenshown and described in some detail, there is no intention to therebylimit the invention to such specific form or the particular employmentshere indicated. On the contrary, the intention is to cover allmodifications and alternative arrangements falling within the spirit andscope of the present invention as expressed in the appended claims.

What is claimed is:

1. In a vehicle and ground-working implement arrangement with eachhaving a supporting framework, and hitch means connecting saidframeworks in draft-receiving and transmitting relation, the combinationof draft sensing means telescopingly mounted on said hitch means andincluding an auxiliary piston and cylinder operative for creatingpressure differentials between opposite ends thereof in response todraft-produced changes in stress in the hitch means, said hitch meansincluding a linkage member pivotally connected at a forward end thereofto the vehicle framework for movement in a horizontal plane andpivotally connected at a rearward end thereof to the implement frameworkthereby to accommodate vertical movement of the implement relative tothe linkage member, a hydraulic actuator mounted on one of saidsupporting frameworks and operative for raising and lowering theassociated implement, said actuator including control valve meansactuable for controlling the operation thereof, draft-signaling meansmounted on one of said frameworks, conduit means communicativelyinterconnecting said draft-sensing and said draft-signaling means andincluding hydraulic fluid therein, said draft signaling means havingmeans therein variably positionable in accordance with the pressuredifferentials created between opposite ends of said auxiliary cylinderas a result of variations in draft load imposed on the tractor by theattached implement, and movement-transmitting means interconnectedbetween said draft-signaling means and said actuator control valve meansand operatively responsive to movements of said variably positionablemeans for actuating said actuator control valve means to selectivelyeffect a raising and lowering of the attached implement and thereby tomaintain a substantially constant draft thereon.

2. In a vehicle and ground-working implement arrangement with eachhaving a supporting framework, and hitch means connecting saidframeworks in draft-receiving and transmitting relation, the combinationof a draft sensing means telescopingly mounted in said hitch meansintermediate opposite ends thereof and exteriorly of the vehicle andincluding expandable and contractible hydraulic motor means operativefor creating pressure differentials proportional to the draft loadbetween opposite ends thereof in response to draft-produced changes instress in the hitch means, said hitch means including a linkage memberpivotally connected at a forward end thereof to the vehicle frameworkfor movement in a horizontal plane and pivotally connected at a rearwardend thereof to the implement framework thereby to accommodate verticalmovement of the implement relative to the linkage member, a hydraulicactuator mounted on one of said supporting frameworks and operative forraising and lowering the associated implement, said actuator includingcontrol valve means actuable for controlling the operation thereof,draft-signaling means mounted on one of said frameworks, conduit meanscommunicatively interconnecting said draft-sensing and saiddraft-signaling means and including hydraulic fluid therein, saiddraft-signaling means having means therein variably positionable inaccordance with the pressure differentials created between opposite endsof said hydraulic motor means as a result of variations in draft loadimposed on the tractor by the attached implement, andmovement-transmitting means interconnected between said draft-signalingmeans and said actuator control valve means and operatively responsiveto movements of said variably positionable means for actuating saidactuator control valve means to selectively effect a raising andlowering of the attached implement and thereby to maintain asubstantially constant draft thereon.

3. In a vehicle and ground-working implement arrangement with eachhaving a supporting framework and being interconnected, the combinationof a draft sensing means having one end thereof pivotally connected tothe vehicle framework and another end thereof pivotally connected to theimplement framework, and being telescopingly operative in draftreceiving and transmitting relation therebetween, said sensing meansincluding expandable and contractible hydraulic motor means operativefor creating pressure differentials proportional to the draft loadbetween opposite ends thereof in response to draftproduced changes instress in said sensing means, a hydraulic actuator mounted on theimplement framework and operative for raising and lowering theassociated implement, said actuator including control Valve meansactuable for controlling the operation thereof, draft-signaling meansmounted on one of said frameworks, conduit means communicativelyinterconnecting said draftsensing and said draft-signaling means andincluding hydraulic fluid therein, said draft-signaling means havingmeans therein variably positionable in accordance with the pressuredifferentials created between opposite ends of said hydraulic motormeans as a result of variations in draft load imposed on the tractor bythe attached implement, and movement-transmitting means interconnectedbetween said draft-signaling means and said actuator control valve meansand operatively responsive to movements of said variably positionablemeans for actuating said actuator control valve means to selectivelyeffect a raising and lowering of the attached implement and thereby tomaintain a substantially constant draft thereon.

4. The invention according to claim 3 and further characterized in thatthe draft-signaling means is mounted on the implement framework in closeassociation with the control valve means of said hydraulic actuator.

5. The invention according to claim 3 and further characterized in thatsaid draft sensing means constitutes the sole draft-receiving andtransmitting connection between the vehicle and implement frameworks.

6. In a vehicle and ground-working implement arrangement with eachhaving a supporting framework and being interconnected, the combinationof a draft sensing means having one end thereof pivotally connected tothe vehicle framework and another end thereof pivotally connected to theimplement framework and being telescopingly operative in draft receivingand transmitting relation therebetween, said sensing means includingexpandable and contractible hydraulic motor means operative for creatingpressure differentials proportional to the draft load between oppositeends thereof in response to draftproduced changes in stress in saidsensing means, a hydraulic actuator mounted on the implement frameworkand operative for raising and lowering the associated implement, saidactuator including control valve means actuable for controlling theoperation thereof, draft-signaling means mounted on one of saidframeworks, conduit means communicatively interconnecting saiddraft-sensing and said draft-signaling means and including hydraulicfluid therein, said draft-signaling means having means therein variablypositionable in accordance with the pressure differentials createdbetween opposite ends of said hydraulic motor means as a result ofvariations in draft load imposed on the tractor by the attachedimplement, and movement-transmitting means interconnected between saiddraft-signaling means and said actuator control valve means andoperatively responsive to movements of said variably positionable meansfor actuating said actuator control valve means to selectively effect araising and lowering of the attached implement and thereby to maintain asubstantially constant draft thereon, and means including a by-passvalve communicatively connected between opposite ends of said hydraulicmotor means and manual means for operating said by-pass valve toestablish free fluid communication between the opposite ends of saidhydraulic motor means whereby the effective length of said draft sensingmeans of which said hydraulic motor means forms a part may be varied.

7. The invention according to claim 3 further characterized in that saidmovement-transmitting means includes lost motion means and means foradjusting said latter means whereby said lost means is positionablyadjustable to a position such that no movement of the variablypositionable means are transmitted to said control valve means, andfurther in that said movement-transmitting means includes manuallyadjustable means operative to effect actuation of said actuator controlvalve means to cause a raising and lowering of the attached implementindependent of movements of the variably positionable means of saiddraft-signaling means.

8. In a vehicle and ground-working implement arrangement with eachhaving a supporting framework and being interconnected, the combinationof a draft sensing mechanism having one end thereof pivotally connectedto the vehicle framework and another end thereof pivotally connected tothe implement framework, and being telescopingly operative in draftreceiving and transmitting relation therebetween; said sensing mechanismincluding expandable and contractible hydraulic motor means operativefor creating pressure differentials proportional to the draft loadbetween opposite ends thereof in response to draft-produced changes instress in said sensing mechanism; a hydraulic actuator mounted on theimplement framework and operative for raising and lowering theassociated implement; said actuator including control valve meansactuable for controlling the operation thereof; a hydraulic displacementdevice supportably carried by the implement framework and fashioned toprovide a bore therein and having a piston variably positionable withinsaid bore, and having a plunger portion of said piston extendingoutwardly of said device; conduit means including a supply of hydraulicfluid therein communicatively interconnecting opposite ends of saidhydraulic motor means and said bore; said displacement device piston andplunger being variably positionable in said bore in accordance with thepressure differentials created between opposite ends of said hydraulicmotor means; motion transmitting means connected with the outwardlyextending plunger portion of said displacement device piston and withsaid actuator control valve means and operative for transmitting thevariably positionable movements of said piston and plunger within saidbore to said actuator control valve means for actuating said lattermeans to effect through operation of said hydraulic actuator a raisingand lowering of the attached implement to thereby maintain asubstantially constant draft on the implement.

9. In a vehicle and ground-working implement arrangement with eachhaving a supporting framework and being interconnected, the combinationof a draft sensing mechanism having one end thereof pivotally connectedto the vehicle framework and another end thereof pivotally connected tothe implement framework, and being telescopingly operative in draftreceiving and transmitting relation t'herebetween; said sensingmechanism including expandable and contractible hydraulic motor meansoperative for creating pressure differentials proportional to the draftload between opposite ends thereof in response to draft-produced changesin stress in said sensing mechanism; a hydraulic actuator mounted on theimplement framework and operative for raising and lowering theassociated implement; said actuator including control valve meansactuable for controlling the operation therea yd au ic displacementdevice supportably carried l? by the implement framework and fashionedto provide a bore therein and having a piston variably positionablewithin said bore, and having a plunger portion of said piston extendingoutwardly of said device; conduit means including a supply of hydraulicfluid therein communica tively interconnecting opposite ends of saidhydraulic motor means and said bore; said displacement device piston andplunger being variably positionable in said bore in accordance with thepressure differentials created between opposite ends of said hydraulicmotor means; motion-transmitting means interposed between said hydraulicdisplacement device and said actuator control valve means and includingmanually adjustable cam means, and means interconnecting the outwardlyextending plunger portion of said displacement device with said cammeans, link means connected at one end thereof to said actuator controlvalve means and having another end thereof disposed for contactingengagement with said cam means, said cam means being adjustable to aplurality of positions in certain of which positions said cam means iseffective for transmitting movements of the variably positionable pistonof said hydraulic device to said actuator control valve means foractuating said latter means to effect at raising and lowering of theattached implement to thereby maintain a substantially constant draft onthe implement and in certain other positions thereof said cam means iseffective for interrupting the transmission of movements between saidvariably positionable piston and said actuator control valve means.

References Cited by the Examiner UNITED STATES PATENTS 7/1956 Altgeltl729 3/1961 Fletcher 1727

1. IN A VEHICLE AND GROUND-WORKING IMPLEMENT ARRANGEMENT WITH EACHHAVING A SUPPORTING FRAMEWORK, AND HITCH MEANS CONNECTING SAIDFRAMEWORKS IN DRAFT-RECEIVING AND TRANSMITTING RELATION, THE COMBINATIONOF DRAFT SENSING MEANS TELESCOPINGLY MOUNTED ON SAID HITCH MEANS ANDINCLUDING AN AUXILIARY PISTON AND CYLINDER OPERATIVE FOR CREATINGPRESSURE DIFFERENTIALS BETWEEN OPPOSITE ENDS THEREOF IN RESPONSE TODRAFT-PRODUCED CHANGES IN STRESS IN THE HITCH MEANS, SAID HITCH MEANSINCLUDING A LINKAGE MEMBER PIVOTALLY CONNECTED AT A FORWARD END THEREOFTO THE VEHICLE FRAMEWORK FOR MOVEMENT IN A HORIZONTALLY PLANE ANDPIVOTALLY CONNECTED AT A REARWARD END THEREOF TO THE IMPLEMENT FRAMEWORKTHEREBY TO ACCOMMODATE VERTICAL MOVEMENT OF THE IMPLEMENT RELATIVE TOTHE LINKAGE MEMBER, A HYDRAULIC ACTUATOR MOUNTED ON ONE OF SAIDSUPPORTING FRAMEWORKS AND OPERATIVE FOR RAISING AND LOWERING THEASSOCIATED IMPLEMENT, SAID ACTUATOR INCLUDING CONTROL VALVE MEANSACTUABLE FOR CONTROLLING THE OPERATION THEREOF, DRAFT-SIGNALING MEANSMOUNTED ON ONE OF SAID FRAMEWORKS, CONDUIT MEANS COMMUNICATIVELYINTERCONNECTING SAID DRAFT-SENSING AND SAID DRAFT-SIGNALING MEANS ANDINCLUDING HYDRAULIC FLUID THEREIN, SAID DRAFT SIGNALING MEANS HAVINGMEANS THEREIN VARIABLY POSITIONABLE IN ACCORDANCE WITH THE PRESSUREDIFFERENTIALS CREATED BETWEEN OPPOSITE ENDS OF SAID AUXILIARY CYLINDERAS A RESULT OF VARIATIONS IN DRAFT LOAD IMPOSED ON THE TRACTOR BY THEATTACHED IMPLEMENT, AND MOVEMENT-TRANSMITTING MEANS INTERCONNECTEDBETWEEN SAID DRAFT-SIGNALING MEANS AND SAID ACTUATOR CONTROL VALVE MEANSAND OPERATIVELY RESPONSIVE TO MOVEMENTS OF SAID VARIABLY POSITIONABLEMEANS FOR ACTUATING SAID ACTUATOR CONTROL VALVE MEANS TO SELECTIVELYEFFECT A RAISING AND LOWERING OF THE ATTACHED IMPLEMENT AND THEREBY TOMAINTAIN A SUBSTANTIALLY CONSTANT DRAFT THEREON.